1. Field of the Invention
The present invention relates to a new left ventricular thermodilution catheter devised to evaluate the global ejection fraction during diagnostic and interventional catheterization.
2. Description of the related art including information disclosed under 37 CFR .sctn..sctn.1.97-1.99
Attempts to measure cardiac output started late last century with Stewart's first determination of this value using continuous injection of hypertonic saline as an indicator and obtaining an auditory signal During the following decades, several other continuous and single injection indicator dilution techniques to measure cardiac output of the right and left ventricles both at rest and during exercise were developed and widely applied. These methods have the minute volume of cardiac output as their common objective. They do not proceed to realize the more specific value of ventricular function, namely, ventricular ejection fraction, particularly that of the left ventricle, which is the ratio of the stroke volume of the left ventricle over end-diastolic volume of the left ventricle. The left ventricular ejection fraction is the global index of fiber shortening and is now considered to be one of the most sensitive values of left ventricular function.
Accurate determination of the global ejection fraction of the left ventricle has become a practical step to obtain an over all function of the left ventricle. Further measures to obtain segmental and regional values may not always be required. Present diagnostic values used to determine the left ventricular ejection fraction include, two dimensional echocardiography, digital angiography, contrast ventriculography and radionuclide ventriculography. More recently, ultra fast computed tomography and nuclear magnetic resonance were adapted to measure these values. With the exception of two dimensional echocardiography, all other sophisticated systems are only available in specialized centers.
Ejection fraction measures by two dimensional echocardiography carry with them a significant percentage of error. This appears while measuring the basal portion of the ventricle with a gradually more acutely directed angle relative to the long axis of the ventricle. The progressively more oblique angles underestimate the normal apex to base segmental variability.